The present invention relates to an inside contamination prevention structure for an image formation apparatus utilizing a so-called electrophotographic system for preventing contamination inside the apparatus due to discharged toner leaking from an opening of a discharged toner container.
An image formation apparatus such as an electronic copy machine, a laser printer and the like which uses a so-called electrophotographic system is known, the image formation apparatus forming an electrostatic latent image by exposing a surface composed of a photoconductive material of a photoconductive drum which has been charged in advance with a predetermined polarity, developing the latent image by adhering toner particles on the photoconductive drum in accordance with the latent image, and transferring the toner image onto a recording medium and fixing a same at a fixing unit.
FIG. 1 shows a diagram of the schematic arrangement of a laser beam printer. A cleaning unit 2, a discharging unit, 3, a charging unit 4, scanning optical system 5 for introducing a laser beam having been modulated in accordance with an image information onto a photoconductive drum 1, as indicated by an arrow "A", a development unit 6, and a transfer unit 7 are disposed, respectively, around the photoconductive drum 1 in a rotational direction "B" thereof. Further, a fixing unit 8 is disposed at the downstream side of the photoconductive drum 1 along a feeding path of a continuous-form sheet 200.
As the photoconductive drum 1 is rotated in the "B" direction, the surface thereof is, first, evenly charged at the charging unit 4 with a predetermined polarity, and is scanned in a lengthwise direction thereof by the laser beam from the scanning optical system 5. As a result, a latent image corresponding to the image information to be developed is formed on the photoconductive drum 1. Toner is adhered to the latent image at the development unit 5 to make the latent image visible as a toner image, and the toner image is transferred onto the recording paper 200 being fed at the speed same as the circumferential speed of the photoconductive drum 1 being rotated at the transfer unit 7. The toner image transferred onto the recording paper 200 is heated and pressurized at the fixing unit 8. Thus the transferred toner image is fixed onto the recording paper 200.
The photoconductive drum 1 must be replaced each predetermined operation time as determined by the life of the photoconductive material thereof, and in many cases the photoconductive drum 1 is integrally arranged with the functional units, such as the cleaning unit 2, charging unit 4 and the like which also have a predetermined positional relationship with respect to the photoconductive drum 1, to thereby form a drum unit.
The cleaning unit 2 cleans the surface of the photo-conductive drum 1 by magnetically or mechanically recovering toner particles remaining on the surface of the photoconductive drum 1 after the toner image has been transferred, and the toner recovered at the cleaning unit 2 is fed to the side of the drum unit in a predetermined manner, and recovered into a discharged toner container not shown.
The charging unit 4 usually charges the photoconductive drum 1 with a so-called corona discharge generated by a corona charger (not shown) since harmful ozone is generated by the corona discharge, the image formation apparatus utilizing an electrophotographic system is usually provided with a filter for absorbing the ozone and a fan for introducing air in the apparatus to the filter, so that the ozone is absorbed by the filter.
To effectively absorb the generated ozone by the filter the positional relationship between air intake ports and the fan is preferably set to enable air to flow along the charging unit, for this purpose, the air intake ports must be disposed at the upper portion of one end of the charging unit and the fan must be disposed at the other end of the charging unit, so that the air taken from the air intake ports flows along the charging unit.
However, when it is intended that the air intake ports are disposed at the upper portion of one end of the charging unit and the fan is disposed at the other end of the charging unit, as described above, the fan cannot help being disposed at the other end of the charging unit because the discharged toner container must be disposed at the one end of the charging unit. Thus the air intake ports must be defined on the discharged toner container side. In other words, air entering from the air intake port passes over the discharged toner container and then reaches the filter passing over the discharging unit.
As a result, a problem arises in that floating toner dust, leaking from the discharged toner container, flows into the apparatus together with air and contaminates the inside thereof.
This problem can be prevented by completely sealing the opening of the discharged toner container with a cover as an independent member. However, when discharged toner is to be removed, the mounting and dismounting operations of the cover is time consuming and there is a great possibility that the cover is left to be mounted or lost.